Floppy drive pin 2 question?
ard at p850ug1.demon.co.uk
Mon Mar 14 17:13:13 CST 2005
> I have tried to research the issue further but can I find no authoritative
> references to pin 2 being anything but an RPM select line.
> Other websites like mine do claim it is use for write current but provide no
> references to show it.
The IBM PC/AT Options and Adapters Techref supplement (what a title!)
contains a section on the 'High Capacity Diskette Drive'. It defines pin2
as '-Reduced write' (the leading '-' meaning active low) and devines it
as 'The inactive state of this signal indicates that high-density media
is present requiring normal write currents, and the active state
indicates low-density media is present, requiring a reduced write current.'
The schematics only show the logic board, not the spindle motor, but I
can fiond no speed-control connection to the spindle motor on the
diagram. I can find a circuit connected to pin 2 of the interface
connector that will control the write current.
I have no evidence that this was ever used in a production drive, of
course, but there is a document that supports that pin 2 is used to
control the write current.
More information about the cctalk